a. Field of the Invention
This invention relates to a system and method for controlling delivery of ablation energy by an ablation catheter to tissue in a body. In particular, the instant invention relates to a system and method that enable fine control or titration of the delivery of ablation energy to tissue in response to changes in various characteristics associated with the delivery of ablation energy to the tissue such as the degree of contact between the ablation catheter and tissue.
b. Background Art
It is well known to use ablation catheters to create tissue necrosis in cardiac tissue to correct cardiac arrhythmias (including, but not limited to, atrial fibrillation, atrial flutter, atrial tachycardia and ventricular tachycardia). Arrhythmia can create a variety of dangerous conditions including irregular heart rates, loss of synchronous atrioventricular contractions and stasis of blood flow which can lead to a variety of ailments and even death. It is believed that the primary cause of many arrhythmias is stray electrical signals within one or more heart chambers. The ablation catheter imparts ablative energy (e.g., radiofrequency energy, light energy, ultrasound, or thermal (cryo or heat based) energy) to the heart tissue to create a lesion in the heart tissue. This lesion disrupts undesirable electrical pathways and thereby limits or prevents stray electrical signals that lead to arrhythmias.
Ablation therapy provides significant benefits in resolving cardiac arrhythmias. There are, however, a number of risks associated with ablation therapy. The use of certain types of ablative energy (e.g. radiofrequency energy) generates heat that can lead to formation of a thrombus at or near the distal tip of the catheter. If the thrombus becomes dislodged, there is a risk that the thrombus will travel to a location where the thrombus will prevent further bloodflow and result in stroke. Many catheters employ saline irrigation to cool the tip of the catheter, but irrigation may fail to sufficiently reduce heat and thrombus formation. Thrombii may also be removed by employing vacuum force through the sheath in which the catheter is disposed or by removing the catheter itself, but both of these actions may result in dislodgement of the thrombus.
The foregoing discussion is intended only to illustrate the present field and should not be taken as a disavowal of claim scope.